“On April 13, 2012, our information security team confirmed the presence of a computer virus on our network and immediately took aggressive actions to protect the company’s systems and data. This included actions to protect information related to customers, employees and other partners worldwide. This incident initially involved the malicious placement of malware within our IS network, which then allowed transfer from a data store, housing employee user account credentials.

“As a result of our swift and deliberate actions we believe that our systems are secure and that no customer, employee or program data has been compromised. However, we believe that user IDs and hashed passwords were transmitted. We have no indication that any personal information and emails have been compromised. Regardless, we are continuing to take appropriate precautionary measures.

“Due to the ever-evolving sophistication and tenacity of hackers targeting corporations and governments on a daily basis, we continue to vigilantly maintain our protection and detection systems and related countermeasures to keep ahead of emerging threats. Our focus remains on safeguarding the integrity of employee, consumer and corporate information.”

Nissan said it opted to keep the hack secret for the last 10 days until it had a better idea what was going on, a spokesman said.